How to Valorize Peanut Shells by a Simple Thermal-Catalytic Method

In this work, a simple thermal-catalytic system was used to valorize peanut shells (Arachis hypogaea), the residual biomass from the peanut industry. To accomplish this purpose, tin modified MEL zeolites were synthesized to catalyze pyrolysis vapors reactions in order to improve bio-oil quality. The processes were conducted at 500 °C for 10 min, with biomass-to-catalyst ratio of 1:1. Proximate, ultimate and elemental analyses of the peanut shells were carried out. Biopolymer composition and HHV were also determined. Thermal decomposition behavior of the raw material was assessed by TGA/DTG analysis. Tin was incorporated to the zeolite matrix by the wet impregnation method to obtain loads of 2, 5, 7 and 10 wt%. All the catalysts were characterized by XRD, TPR, FTIR and BET surface area. Liquid products composition was determined by GC–MS. The material with 5 wt% of tin showed the best results. The optimal combination of Lewis and Bronsted acid sites in this catalyst promoted the necessary reactions to enhance bio-oil quality. In this sense, hydrocarbons selectivity in the presence of the 5 wt% tin zeolite was ten times the one reached in the absence of catalysts. Likewise, 5-hydroxymethyl-furfural formation was favored, obtaining the highest selectivity with the same metal load on the catalyst.